Fiber optic cables include one or more optical fibers or other optical waveguides that conduct optical signals, for example carrying voice, data, video, or other information. In a typical cable arrangement, optical fibers are placed in a tubular assembly. A tube may be disposed inside an outer jacket or may form the outer jacket. In either case, the tube typically provides at least some level of protection for the fibers contained therein.
Optical fibers are ordinarily susceptible to damage from water and physical stress. Without an adequate barrier, moisture may migrate into a fiber optic cable and weaken or destroy the cable's optical fibers. Without sufficient physical protection, stress or shock associated with handling the fiber optic cable may transfer to the optical fibers, causing breakage or stress-induced signal attenuation.
One conventional technique for protecting the optical fibers from damage is to fill the cable with a fluid, a gel, a grease, or a thixotropic material that strives to block moisture incursion and to absorb mechanical shock. Such fluids and gels are typically messy and difficult to process, not only in a manufacturing environment but also during field service operations. Field personnel often perform intricate and expensive procedures to clean such conventional materials from optical fibers in preparation for splicing, termination, or some other procedure. Any residual gel or fluid can render a splice or termination inoperably defective, for example compromising physical or optical performance.
Another conventional technology for protecting optical fibers entails placing a water absorbent chemical, such as water-swellable material, within the cable. The chemical absorbs water that may inadvertently enter the cable, and swells to prevent the water from traveling down long lengths of cable and degrading the delicate optical fibers. In one conventional approach, particles of the water absorbent chemical are mixed with the gel discussed above, and the mixture is inserted into the cable. This approach typically suffers from the same drawbacks as using a pure form of a gel; gels and related materials are messy and difficult to process.
In another conventional approach, a water-swellable chemical is applied to the surface of a tape or a yarn that is inserted in the cable lengthwise. If water enters the cable, the water-swellable chemical interacts with the water and swells to impede and stop water flow lengthwise along the cable. However, conventional tape and yarn technologies typically offer limited protection against incursions of seawater. The salt content of seawater typically reduces the effectiveness of water-swellable chemicals via interfering with the interaction between the seawater and the chemicals.
In many instances, a manufacturer will label a fiber optic cable seawater resistant if the cable can pass a test involving subjecting the cable to a three percent seawater mixture. In such tests, typically three percent of the solution is seawater and the remaining ninety-seven percent is distilled water. Since natural seawater has a salinity of between about three percent and about five percent, such tests provide a salinity of only about 0.09 percent (3% seawater multiplied by 3% salinity equals 0.09% net salinity) and a corresponding specific gravity of only about 1.004.
Withstanding seawater having a three percent salinity is significantly more challenging than withstanding a three percent seawater solution. In an actual field deployment, a fiber optic cable may need to withstand the full, three-to-five percent salinity of seawater. Otherwise, the fiber optic cable may have an increased risk of failure.
Accordingly, to address these representative deficiencies in the art, an improved capability is needed for protecting optical fibers from water damage. Further need exists for a fiber optic cable that can protect optical fibers of a fiber optic cable from seawater or saltwater. A need further exists for a fiber optic cable that can restrict the flow of any saltwater or seawater that might inadvertently enter the cable, to avoid lengthwise progression of unwanted saltwater or seawater. A capability addressing one or more of the aforementioned needs, or some related need in the art, would provide robust fiber optic installments and would promote optical fibers for communications and other applications.